1. Field of the Invention:
The present invention relates to a loudspeaker system or, to say more in detail, a speaker system provided with a sealed type globular enclosure made of glass, which enclosure serves to attach a speaker unit thereto and is placed elastically on a support member.
2. Description of the Related Art:
Recently a speaker system has been proposed in which a speaker unit is attached to a globular enclosure made of glass. As shown in FIG. 1, a speaker unit 3 is attached to the opening 2 of a globular enclosure made of glass 1. From the physical characteristic of glass and from the reason that the enclosure is globular, such a loudspeaker system is excellent in hi-fi reproduction, and a radiation pattern, which expresses the characteristics of a speaker unit most naturally, is possible. Indeed, by making the shape of an enclosure globular, the high frequency wave characteristic of a speaker system becomes flat in wider directions in a room, and further, with the use of glass, not only the production of a globular enclosure is easy but also a heavy, hard and thick enclosure, which are the basic requisites to repress the vibration of the enclosure itself, can easily be produced, thus increasing the oscillation-damping characteristic of a speaker system remarkably.
However, in such a speaker system, from the reason that the enclosure 1 is globular and the speaker unit 3 is attached part from the center of the enclosure 1, there is a drawback that the enclosure rolls on the floor, and thus it is impossible to maintain the speaker unit to a definite direction correctly. Thus, it is necessary to put the speaker system on a support member prepared particularly.
In FIG. 1, 4 is an example of the conventional support member for this use. The support member 4 is of a box type having its opening at the upper side, and a felt sheet 5 is attached to the edge part of the opening for preventing that the enclosure receives a shock in mounting the speaker system thereon and that the outer face of the enclosure 1 is damaged.
In such a type of support member, however, while it is possible to change the direction of the speaker unit 3 freely, the friction coefficient is as small as 0.36 between the surface of the enclosure 1 and the felt sheet 5 which is attached to the edge part of the opening of the support member 4 on which the enclosure 1 is to be mounted, and accordingly, in the case, for instance, when vibration is given to the support member 4 from outside, the enclosure 1 may rotate due to the moment caused to occur owing to the weight of the speaker unit 3 of it own, changing frequently the direction of the speaker unit 3.
Further, in a speaker system with the use of a globular enclosure made of glass, while the occurrence of so-called box noise, which is caused to occur due to the vibration of the enclosure, which is accompanied by the action of the speaker unit owing to the sound signal, can tolerably be prevented, the prevention is not perfect. The occurrence of box noise is due to the reason that the enclosure itself is resonated with the sound of the speaker unit to form a noise so-called body noise, and the resonance frequency is determined from such factors as the composition (density) and thickness of the glass as well as the enclosure shape and size. Therefore, to repress box noise, it is necessary to make the body noise as small as possible and to damp this noise in a short time.
It is said that there are two causes for the box noise of a speaker system. The one is the compression and expansion of air in the enclosure due to the movement of the cone paper of the speaker unit, and the other is the vibration of the enclosure itself due to the speaker unit's oscillation, which is transmitted through the frame of the speaker unit. The former gives chiefly low sounds, and the latter chiefly medium-high sounds to the enclosure. In a speaker system comprising a globular glass enclosure, the difficulty due to the former reason has almost been dissolved by making the enclosure heavy and rigid and by the proper disposition of a sound absorption material.
However, there is a danger that the support member 4 acts as a resonance box. For preventing the support member from serving as a resonance box and thus to prevent the occurrence of box- or body noise from this reason, while it is desirable to fill up the interior of the support member 4 with a solid matter, it is impossible to produce a perfectly globular enclosure made of glass with a constant outer diameter, forming fluctuation to some extent, from the difficulty in the manufacturing process of globular glass, and therefore, it is difficult to contact the convex-type outer circumference of the enclosure 1 totally with the concave-type inner circumference of the support member 4.
Moreover, in fixing a speaker unit directly to a glass enclosure by using a screw, stress is accumulated at the edge part of the enclosure opening, and there is a danger that said edge part is broken. Therefore, it has been proposed to fix an annular flat plate to serve as a baffle board to the opening of the enclosure with the use of an adhesive, and then to fasten a speaker unit to said baffle board with the use of a screw. In this instance, however, attention has been paid only on the use of an annular flat plate for attaching the speaker unit easily to the enclosure, and accordingly a cheap and easily obtainable material such as aluminium, wood or acrylic resin has been used therefor. Therefore, because of the fact that these materials are inferior in rigidity and oscillation-damping property, they are not sufficient to prevent the occurrence of box noise due to the latter reason, and further, the occurrence of body noise due to the deformation of the enclosure opening can not sufficiently be prevented.
Separately, for the purpose of enhancing the decorative effect of a speaker system with the use of a glass enclosure, a speaker system has been proposed in which a light source is provided in the interior of an enclosure on one hand and, on the other hand, an amplifying circuit is provided from the outside of the enclosure for changing the brightness of the light source in accordance with the change of the quality and tone of the sound. However, in putting a light source in the interior of an enclosure, not only the capacity of the enclosure is diminished, but also the sound quality is deteriorated due to such factors as the heating of the enclosure and the interference to the sound signal caused to occur due to the light source. Further, it is necessary thereby to make a hole in the enclosure for the wiring to the light source. There is also a trouble to remove the speaker unit from the enclosure at the time when the light source must be exchanged due to its life.